It is somewhat of a mistake to paint all libertarians with one brush. Whereas there are those who simply believe that unfettered markets will maximize overall utility, there are also those who are more principled in their libertarianism and base their ideology around the notion of respect for freedom as the benchmark of justice. The most famous work of libertarian philosophy (with the possible exceptions of Hayek's Road to Serfdom and Constitution of Liberty) is arguably Nozick's "Anarchy State and Utopia", and Nozick argues for unfettered markets not because of what such markets might produce (in fact, he objects to all "end-state principles" in determining just economic arrangements) but beause of what such state-intervention consists in: injustice (he says that redistributive taxation is just like forced labor). Obviously, that thesis cannot be empirically refuted: as the old Roman proverb has it, justice must be done though the heavens(/Dow) fall. It is also important to understand that most libertarians like to combine the view that state interference is inherently unjust with the view that it is sub-optimal, and that people do not easily give up ideologies: hence, we might expect to see more and more attention paid to Nozickian forms of 'principled libertarianism'. Either way, libertarianism is not going to go away.